1. Field of the Invention
The present invention relates to a dispenser for a liquid crystal display panel and a method for controlling a gap distance between a nozzle and a substrate when using the dispenser, and more particularly, to a dispenser for a liquid crystal display panel and a method for controlling a gap distance between a nozzle and a substrate when using the dispenser to control a gap distance between the substrate, where a liquid crystal display panel is formed, and the nozzle.
2. Discussion of the Related Art
In general, a liquid crystal display device is a display device where data signals according to picture information are individually supplied to liquid crystal cells arranged in a matrix form. Light transmittance of the liquid crystal cells is controlled in accordance with the data signals to display a desired picture. The liquid crystal display device includes a liquid crystal display panel where the liquid crystal cells are arranged in a matrix form, and a driver integrated circuit (IC) for driving the liquid crystal cells. The liquid crystal display panel includes a color filter substrate and a thin film transistor array substrate attached to each other. The liquid crystal display panel further includes a liquid crystal layer between the color filter substrate and the thin film transistor array substrate.
Data lines and gate lines are formed on the thin film transistor array substrate of the liquid crystal display panel and cross each other at right angles so as to define liquid crystal cells. The data lines transmit a data signal supplied from the data driver integrated circuit to the liquid crystal cells. The gate lines transmit a scan signal supplied from the gate driver integrated circuit to the liquid crystal cells. At an end portion of each of the data lines and the gate lines, a data pad and a gate pad are respectively provided in which data signals and scan signals are respectively applied from the data driver integrated circuit and the gate driver integrated circuit. The gate driver integrated circuit sequentially supplies a scan signal to the gate lines so that the liquid crystal cells arranged in a matrix form can be sequentially selected line by line while a data signal is supplied to the selected line of the liquid crystal cells from the data driver integrated circuit.
A common electrode and a pixel electrode are respectively formed on the inner side of the color filter substrate and the thin film transistor array substrate for applying an electric field to the liquid crystal layer of a liquid crystal cell. More particularly, a pixel electrode is respectively formed in each liquid crystal cell on the thin film transistor array substrate, while the common electrode is integrally formed across the entire surface of the color filter substrate. Therefore, by controlling a voltage applied to the pixel electrode while a voltage is applied to the common electrode, light transmittance of the liquid crystal cells can be individually controlled. To control the voltage applied to the pixel electrode by liquid crystal cells, a thin film transistor is formed in each liquid crystal cell and used as a switching device.
FIG. 1 is a plane view of the unit liquid crystal display panel formed by a thin film transistor array substrate and a color filter substrate according to the related art. As shown in FIG. 1, the liquid crystal display panel 100 includes an image display part 113 where the liquid crystal cells are arranged in a matrix form, a gate pad part 114 connected to the gate lines of the image display part 113, and a data pad part 115 connected to the data lines of the image display part 113. The gate pad part 114 and the data pad part 115 are formed along an edge region of the thin film transistor array substrate 101, which does not overlap with the color filter substrate 102. The gate pad part 114 supplies a scan signal from the gate driver integrated circuit to the gate lines of the image display part 113, and the data pad part 115 supplies image information from the data driver integrated circuit to the data lines of the image display part 113.
Data lines to which image information is applied and gate lines to which a scan signal is applied are provided on the thin film transistor array substrate 101. The data lines and the gate lines cross each other. Additionally, a thin film transistor for switching the liquid crystal cells is provided at each crossing of the data lines and the gate lines. A pixel electrode for driving the liquid crystal cells is connected to the thin film transistor and provided on the thin film transistor array substrate 101. A passivation film for protecting the pixel electrode and the thin film transistor is formed at the entire surface of the thin film transistor array substrate 101.
Color filters are provided on the color filter substrate 102 for each cell region. The color filters are separated by a black matrix. A common transparent electrode is also provided on the color filter substrate 102.
A cell gap is formed by a spacer between the thin film transistor array substrate 101 and the color filter substrate 102. A seal pattern 116 is formed along an outer edge of the image display part 113. The thin film transistor array substrate 101 and the color filter substrate 102 are attached by the seal pattern 116 to thereby form a unit liquid crystal display panel.
In fabricating the unit liquid crystal display panel, a method for simultaneously forming unit liquid crystal display panels on a large-scale mother substrate is generally used. Thus, a process is required for separating the unit liquid crystal display panels from the large-scale mother substrate. For example, a cutting process can be used on the mother substrate to separate the plurality of unit liquid crystal display panels formed thereon.
The seal pattern 116, as discussed above, has an opening. After the unit liquid crystal display panel is separated from the large-scale mother substrate, liquid crystal is injected through a liquid crystal injection opening to form a liquid crystal layer at the cell-gap, which separates the thin film transistor array substrate 101 and the color filter substrate 102. Then, the liquid crystal injection opening is sealed.
As mentioned above, the following steps are required to fabricate the unit liquid crystal display panel: the thin film transistor array substrate 101 and the color filter substrate 102 are separately fabricated on the first and second mother substrates, the first and second mother substrates are attached in such a manner that a uniform cell-gap is maintained therebetween, the attached first and second mother substrates are cut into unit panels, and then liquid crystal is injected to the cell-gap between the thin film transistor array substrate 101 and the color filter substrate 102. In particular, the process of forming the seal pattern 116 along an outer edge of the image display part 113 is required to attach the thin film transistor array substrate 101 and the color filter substrate 102. The related art process of forming a seal pattern will now be described.
FIGS. 2A and 2B illustrate a screen printing method to form a seal pattern. As shown in FIGS. 2A and 2B, there is provided a screen mask 206 patterned so that a of seal pattern forming region is exposed. A rubber squeegee 208 is used to selectively supply a sealant 203 to the substrate 200 through the screen mask 206 so as to simultaneously form a seal pattern 216. The seal pattern 216 formed on the substrate 200 creates a gap in which liquid crystal layer is later injected and prevent leakage of the liquid crystal. Thus, the seal pattern 216 is formed along each outer edge of the image display part 213 of the substrate 200 and liquid crystal injection opening 204 is formed for the seal pattern 216.
The screen printing method includes: applying the sealant 203 on the screen mask 206 with the seal pattern forming region patterned thereon, forming the seal pattern 216 on the substrate 200 through printing with the rubber squeegee 208; and evaporating a solvent contained in the seal pattern 216 and leveling the pattern. The screen printing method is widely used because it is an easy process. However, the screen printing method is disadvantageous in that sealant 203 is wasted because a lot of sealant is discarded after the squeegee 208 is drawn across the screen mask to form the seal pattern 216. In addition, the screen printing method has a problem in that rubbing of an orientation film (not shown) formed on the substrate 200 can incur defects when the screen mask 206 and the substrate 200 come into contact with each other. These defects will degrade picture quality of the liquid crystal display device.
To overcome the shortcomings of the screen printing method, a seal dispensing method has been proposed. FIG. 3 is an exemplary view of a related art dispensing method for forming a seal pattern. As shown in FIG. 3, while a table 310 with the substrate 300 loaded thereon is moved in forward/backward and left/right directions, a seal pattern 316 is formed along an outer edge of image display part 313 on the substrate 300 by applying a predetermined pressure to syringe 301 filled with a sealant. The seal pattern 316 is sequentially formed for the image display part 313.
In the seal dispensing method, since the sealant is selectively supplied to the region where the seal pattern 316 is to be formed, sealant waste is prevented. In addition, the syringe 301 does not contact the orientation film (not shown) of the image display part 313 of the substrate 300 so that the rubbed orientation film will not be damaged. Thus, picture quality of the liquid crystal display device will be maintained.
In the case of forming the seal pattern 316 on the substrate 300 by using the syringe 301, a technique for precisely controlling a gap distance between the substrate 300 and the syringe 301 is required. That is, if the substrate 300 and the syringe 301 are too close compared to a desired gap distance, the seal pattern 316 formed on the substrate 300 is wide and thin. If, however, the substrate 300 and the syringe 301 are separated too much compared to the desired gap distance, the seal pattern 316 formed on the substrate 300 becomes narrow and may become noncontiguous, which causes a defect in the liquid crystal display device.
If the sealant in the syringe 301 is completely used up while forming a seal pattern, the seal pattern 316 cannot be completely formed. Thus, a syringe 301 should be replaced with another syringe 301 filled with the sealant before it is completely used up. At this time, however, the gap distance between the substrate 300 and the syringe 301 varies depending on the syringe 301 in use. Thus, the gap distance between the substrate 300 and a syringe 301 should be reset and/or checked every time a syringe 301 is replaced with a new syringe. Replacement of the syringe 301 is frequently done during actual manufacturing of products. Therefore, a technique for setting or checking the gap distance between the substrate 300 and the syringe 301 within a short time is preferable.
In the related art, a manual operation method has been adopted to control the gap distance between the substrate 300 and the syringe 301, which will now be described in detail. FIG. 4 is an exemplary view showing a seal dispenser of a liquid crystal display panel in accordance with the related art. As shown in FIG. 4, a seal dispenser includes a syringe 403 with a nozzle 402 at one end thereof for supplying a sealant onto a substrate 401 that is loaded onto a table 400, a body 404 for mounting the syringe 403 above the substrate 401, a vertical driving servo motor 405 for moving the body 404 in a vertical direction; a microguage 406 for turning the vertical driving servo motor 405 via manual operation, a first sensor 407 for detecting whether the substrate 401 and the nozzle 402 are in contact with each other; and a second sensor 408 for detecting a gap distance between the substrate 401 and the nozzle 402.
FIG. 5 is a flow chart of a method according to the related art for controlling a gap distance between the nozzle and the substrate by using the seal dispenser of the liquid crystal display panel. As shown in FIG. 5, the method according to the related art for controlling a gap distance between the nozzle and the substrate by using the seal dispenser of the liquid crystal display panel includes lowering the nozzle 402 by manually manipulating the microgauge 406; detecting whether the nozzle 402 and the substrate 401 are in contact with each other; raising the nozzle 402 by manually manipulating the microgauge 406; and stopping the nozzle at the gap distance between the nozzle 402 and the substrate 401.
The related art of the seal dispenser of the liquid crystal display panel and the method for controlling a gap distance between the nozzle and the substrate using the dispenser will now be described in more detail. First, when the substrate 401 is loaded on the table 400, a user turns the vertical driving servo motor 405 by manually manipulating the microgauge 406 to thereby lower the syringe 403 mounted in the body 404. At this time, the user detects whether the nozzle 402 provided at an end portion of the syringe 403 and the substrate 401 loaded on the table 400 are in contact with each other through monitoring of a value measured by the first sensor 407.
When the substrate 401 and the nozzle 402 are detected to be in contact with each other by the first sensor 407, the user turns the vertical driving servo motor 405 by manually manipulating the microgauge 406, thereby raising the syringe 403 mounted in the body 404. At this time, the user detects whether the gap distance between the substrate 401 and the nozzle 402 reaches a desired value through monitoring of a value measured by the second sensor 408 and stops manipulating the microgauge 406 when the value measured by the second sensor 408 reaches a desired value.
The related art of the seal dispenser of the liquid crystal display panel and the method for controlling a gap distance between the nozzle and the substrate have the following problems. First, since the user controls the gap distance between the substrate 401 and the nozzle 402 by manually manipulating the microgauge 406, reliability and consistency are low, which increases the defective occurrence rate in the manufactured liquid crystal display panels. In addition, even a skilled user requires a lot of time to set the gap distance between the substrate 401 and the nozzle 402 precisely, which degrades productivity. Furthermore, since the gap distance is set by the user's manual operation, a strong and constant concentration, which quickly tires users, is required for users to maintain a good process pace.